The present invention is in the field of motorcycle chassis, and pertains more particularly to systems for mounting motorcycle engines to the chassis.
Since the introduction of the first two-wheeled self-propelled motorcycle, which was a converted bicycle with a small, centrally mounted spark ignition engine, many design improvements and other innovations have been incorporated to improve such aspects as speed, power-to-weight ratio, and handling and stability performance. Motorcycles with engines having larger power capacity and engine displacements were increasingly desired early in development because of the increased speed and acceleration capabilities, and required innovative advancements in the technology pertaining to chassis and power train rigidity in order to handle problems caused by greatly increased stresses that could be imposed upon the components during operation of such higher performance motorcycles.
During normal operation of motorcycles the front and rear wheels rotating within the same plane are continually subjected to forces urging them from their proper alignment in order to keep the motorcycle balanced upright within the center of gravity. Even while traveling a straight line the motorcycle must be alternately steered into the direction it is leaning to keep from falling over. The resulting operating loads, although slight during traveling a straight line, are greatly increased during the execution of a turn, becoming quite extreme when the turn is executed at high speeds. Handling and stability can be greatly compromised if the motorcycle chassis does not provide a sufficient level of strength and rigidity.
Much handling and stability performance for a motorcycle is also lost if the suspension of the motorcycle allows the wheels to be excessively forced from their plane of rotation. For example, the rear wheel, rotatably attached to a rigid swing arm having usually a pair of extended arms cantilevered at the rear of the frame, a standard design in the art, is particularly exposed to such forces during high-speed turns. Any excess deflection from its vertical plane during a high-speed turn can seriously impact stability and handling causing an unsafe condition. It is also therefore important to limit, as much as possible, any movement of the rear swing arm that is in a direction other than that within its intended vertical movement.
A maximum level of handling and stability performance is only achieved when deflection as described above is minimized, to the greatest extent possible, by sufficient rigidity designed into the combined functions of the frame, drive train and suspension, so that only minimal deflection by operating loads of the wheels from their proper alignment is allowed. Many methods have been developed, well known in the art, for improving characteristics of strength and rigidity in the chassis, drive train and suspension.
The chassis of most motorcycles is a frame, usually a combination of tubes and sheets most often manufactured of steel that can be arranged in a variety of different design configurations for different styles and types of motorcycles. The frame is preferably designed to have sufficient stiffness and rigidity, particularly in areas of the frame that would endure pronounced stresses during operation of the motorcycle. One method well known in the art of motorcycle frames, and all related structural art, is the use of triangulation and cross support members in the frame design. Another well-known method of supplementing overall chassis rigidity is a method, more commonly used in the past, of incorporation of a rigid engine mounting system whereby the engine itself is rigidly mounted to the frame and becomes a partially-stressed member of the frame, supplementing the overall rigidity of the chassis. Also, more rigid and stronger connections between the engine and transmission have been used in some cases to supplement rigid or semi rigid engine mount systems, increasing the overall collective rigidity of chassis, power train and rear suspension.
Rider comfort also quickly became an item of much attention in early development, leading to the introduction of many related improvements such as, for example, shock absorbing suspension systems for both front and rear wheels, and advancements in technology pertaining to balancing of reciprocal and rotary vibration of engine components, both being methods for reducing the level of road and engine vibration ultimately absorbed by the frame and rider. The engine of any motorcycle must be designed so that the rotary and reciprocal vibration caused by the internal moving parts are balanced to reduce vibration to a level acceptable in accordance with the intended durability of the frame and engine mount system of the motorcycle, coupled with the level of comfort that should be expected by the rider.
Certain classic styles of motorcycles, such as those designed with long, lower-profile frames and large twin-cylinder engines having high displacement, power and torque, have experienced and retained wide and ever-increasing popularity in today""s market. This is largely due to the powerful and nostalgic look and feel, as well as improved performance, comfort and other desirable aspects unique to the style. The cylinders of the engine in such a motorcycle are most often arranged in a vertical xe2x80x9cVxe2x80x9d configuration; hence the name xe2x80x9cV twinxe2x80x9d as is commonly used in reference. The pistons within the cylinders and many other engine components are typically much larger and heavier than those of a common smaller displacement four-cylinder engine, producing a much higher level of vibration when the engine is operated, particularly true when the engine is operating at lower or idle speeds or in a high-torque situation. Such vibration, when not sufficiently isolated, can be extremely injurious to the chassis and components, causing fatigue to the frame and problems such as early weld failure or cracks, and so on, and also can be uncomfortable to the point of unbearable to many riders. A motorcycle engine with more than one cylinder has more than one connection point between piston and crank shaft, causing reciprocal and rotary vibration, always existing to some extent regardless of the level of balancing designed into the moving parts of the engine. Different styles of engines have varying numbers, sizes and configurations of cylinders and therefore generate greatly varying levels of vibration. For example, a motorcycle having a smaller displacement four-cylinder engine with much smaller pistons has, because of its design, smaller and more numerous moving internal components, and when the engine is operating the resulting vibration is less pronounced. Conversely, a large displacement twin cylinder engine such as described earlier has large pistons causing much more pronounced vibration, and when combined with the vibration of the other typically heavier internal components, an excessive amount of vibration can be generated, particularly at idle speeds.
Although significant advancements have been made in technology pertaining to the balancing of reciprocal and rotary vibration of engine components, the basic nature of some engine designs, such as, for example, large-cylinder engines as described above, makes balancing to an acceptable level extremely difficult, at least partly due to the orientation and vertical travel directions of the large pistons within the cylinders, causing, along with other internal components, the rotary and reciprocal vibration. In conventional art manufacturers have attempted to solve the vibration problem by utilizing a variety of methods, such as elastomeric engine mounting systems using soft interfaces of various size and durometer, often manufactured of rubberized or similarly resilient material, for mounting the engine to the frame. Such resilient interfaces can sometimes have different aspects of adjustability, and in typical cases they are used in all of the engine mounting locations, usually located at both the front and rear of the power train, and also at the top in many cases, forming a triangular arrangement between the soft engine mount locations.
Other methods known in the art include mounting the rear suspension and engine unit into a separate rigid power train unit which is attached to the main chassis, or by attaching the rear suspension by a pivot arm to mounting members adapted to receive the ends of the pivot arm, or to a pivot point in the housing of an engine or transmission component which may or may not be rigidly mounted to the frame. Although a significant amount of vibration can be isolated from the frame using such conventional systems, the engine is not allowed to adequately contribute to frame rigidity because all of the engine mounts are still resilient in varying degrees, whether or not they incorporate the swing arm pivot function. Handling and stability is further compromised because the rear wheel can be deflected on at least one axis from the plane of the front wheel. This condition compromises the stability of the motorcycle and adversely affects handling and performance, particularly when the motorcycle is operated in high speed during turns.
Another problem compared with many of these methods is that a pronounced engine vibration is still present as the engine operating frequency increases. In this case an inadequately-isolated vibration can produce an uncomfortable riding condition when the engine is operated at higher frequencies.
The previously described known methods for improving the handling and stability of a motorcycle, while maintaining an acceptable level of comfort to the rider through vibration isolation, have often left unsatisfactory results. In many cases these arrangements have reduced vibration while maintaining chassis and suspension rigidity to acceptable levels in some types of motorcycles, such as those with smaller four-cylinder engines having less engine vibration. However, results obtained by attempting to apply these arrangements to motorcycles with larger twin-cylinder engines with excessive vibration such as described above have been unsatisfactory in conventional art.
When such an engine is operated, the engine vibration is most pronounced at idle speed, and because of the elastomeric engine mounts may also be very pronounced when the engine is operated at higher engine speeds. Attempting to isolate such extreme vibration by using rigid engine mounts such as described is not practical and for this reason conventional design for this style of motorcycle teaches an emphasis on soft motor mounting systems compromising overall stability performance of the chassis, drive train and rear suspension, and allowing unacceptable levels of high-frequency engine vibration to transfer to the frame, causing excess fatigue and possible premature damage to the frame, and greater discomfort and fatigue to the rider.
What is clearly needed is improved method and apparatus for mounting an engine in a motorcycle chassis that provides the best possible combination of dampening the extreme engine vibration at various engine operating frequencies, and significant contribution to the level of stiffness between the chassis, engine and power train, and rear suspension system to minimize unbalancing forces in turns and other maneuvers.
In a preferred embodiment of the present invention a vibration-isolation system for assembly of a motorcycle frame with an engine/transmission unit is provided, comprising a first pivotal mount at a rear portion of the frame and engine/transmission unit, the first mount comprising all rigid bearing components mounted to solid elements of both the frame and the engine/transmission unit, the first mount thereby allowing the engine/transmission unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame; and a second mount at a front portion of the frame and engine/transmission unit, the second mount incorporating one or more elastomeric elements between a solid interface to the frame and a solid interface to the engine/transmission unit, thereby allowing substantially vertical translation of the engine transmission unit relative to the frame at the second mount, the translation of an amplitude limited by the elastomeric elements, and thereby limiting the rotation of the engine/transmission unit around the first pivotal mount.
In some preferred embodiments the bearing components of the first mount comprise one or more journal bearings, while in others the bearing components of the first mount comprise one or more ball bearings. Also in some embodiments the elastomeric elements of the second mount comprise one or more cylinders of rubber-like material. In some cases there is adjustment apparatus associated with the second mount, enabling a user to adjust the elasticity of the second mount to tune vibration effects of the system.
In some embodiments of the invention the cylinders of rubber-like material are mounted on a shaft having an axis, and the second mount includes a compression apparatus allowing compression of the elastomeric elements in the direction of the axis, thereby adjusting the elasticity of the second mount to tune vibration effects of the system.
In another aspect the assembly includes a swing arm for mounting a rear wheel for a motorcycle using the frame and engine/transmission unit, wherein the swing arm mounts pivotally to the second mount integrally with the engine/transmission unit, thereby allowing the swing arm unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame.
In yet another aspect of the invention a method for mounting an engine/transmission unit to a frame for a motorcycle to isolate vibration is provided, comprising steps of (a) mounting the engine/transmission unit to a first pivotal mount at a rear portion of the frame, the first mount comprising all rigid bearing components mounted to solid elements of both the frame and the engine/transmission unit, the first mount thereby allowing the engine/transmission unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame; and (b) mounting the engine/transmission unit to a second mount at a front portion of the frame and engine/transmission unit, the second mount incorporating one or more elastomeric elements between a solid interface to the frame and a solid interface to the engine/transmission unit, thereby allowing substantially vertical translation of the engine transmission unit relative to the frame at the second mount, the translation of an amplitude limited by the elastomeric elements, and thereby limiting the rotation of the engine/transmission unit around the first pivotal mount.
In some embodiment of the method the bearing components of the first mount comprise one or more journal bearings. In other embodiments the bearing components of the first mount comprise one or more ball bearings. In these and other embodiments the elastomeric elements of the second mount may comprise one or more cylinders of rubber-like material.
In some cases of the method there is adjustment apparatus associated with the second mount, enabling a user to adjust the elasticity of the second mount to tune vibration effects of the system.
In some cases the cylinders of rubber-like material are mounted on a shaft having an axis, and the second mount includes a compression apparatus allowing compression of the elastomeric elements in the direction of the axis, thereby adjusting the elasticity of the second mount to tune vibration effects of the system. Also in some cases there may be a swing arm for mounting a rear wheel for a motorcycle using the frame and engine/transmission unit, wherein the swing arm mounts pivotally to the second mount integrally with the engine/transmission unit, thereby allowing the swing arm unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame.
In another aspect of the invention a frame and engine assembly for motorcycle is provided, comprising a frame having a first frame interface for a first mount positioned at the rear and a second frame interface for a second mount positioned at the front; an engine/transmission unit having a first engine/transmission unit interface for the first mount and a second engine/transmission unit for the second mount; and a first mount and a second mount between the frame and the engine/transmission interface.
The assembly is characterized in that the first mount comprises all rigid bearing components mounted to solid elements interfacing to both the frame and the engine/transmission unit, the first mount thereby allowing the engine/transmission unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame, and in that the second mount incorporates one or more elastomeric elements between solid elements interfacing to the frame and to the engine/transmission unit, thereby allowing substantially vertical translation of the engine transmission unit relative to the frame at the second mount, the translation of an amplitude limited by the elastomeric elements, and thereby limiting the rotation of the engine/transmission unit around the first pivotal mount.
In some embodiments the bearing components of the first mount comprise one or more journal bearings, while in others the bearing components of the first mount comprise one or more ball bearings.
In some cases the elastomeric elements of the second mount comprise one or more cylinders of rubber-like material, and in some of these embodiments there is adjustment apparatus associated with the second mount, enabling a user to adjust the elasticity of the second mount to tune vibration effects of the system.
In some embodiments of the invention the cylinders of rubber-like material are mounted on a shaft having an axis, and the second mount includes a compression apparatus allowing compression of the elastomeric elements in the direction of the axis, thereby adjusting the elasticity of the second mount to tune vibration effects of the system.
In some embodiments the assembly includes a swing arm for mounting a rear wheel for a motorcycle using the frame and engine/transmission assembly, wherein the swing arm mounts pivotally to the second mount integrally with the engine/transmission unit, thereby allowing the swing arm unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame.
In yet another aspect of the invention a motorcycle is provided comprising a frame having a first frame interface for a first mount positioned at the rear and a second frame interface for a second mount positioned at the front; an engine/transmission unit having a first engine/transmission unit interface for the first mount and a second engine/transmission unit for the second mount; and a first mount and a second mount between the frame and the engine/transmission interface. This motorcycle is characterized in that the first mount comprises all rigid bearing components mounted to solid elements interfacing to both the frame and the engine/transmission unit, the first mount thereby allowing the engine/transmission unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame, and in that the second mount incorporates one or more elastomeric elements between solid elements interfacing to the frame and to the engine/transmission unit, thereby allowing substantially vertical translation of the engine transmission unit relative to the frame at the second mount, the translation of an amplitude limited by the elastomeric elements, and thereby limiting the rotation of the engine/transmission unit around the first pivotal mount.
In some embodiments of the motorcycle the bearing components of the first mount comprise one or more journal bearings, and in some embodiments the bearing components of the first mount comprise one or more ball bearings.
In some cases the elastomeric elements of the second mount comprise one or more cylinders of rubber-like material. Also in some cases there is further provided adjustment apparatus associated with the second mount, enabling a user to adjust the elasticity of the second mount to tune vibration effects of the system.
In some cases the cylinders of rubber-like material are mounted on a shaft having an axis, and the second mount includes a compression apparatus allowing compression of the elastomeric elements in the direction of the axis, thereby adjusting the elasticity of the second mount to tune vibration effects of the system.
Also in some cases the assembly includes a swing arm for mounting a rear wheel for a motorcycle using the frame and engine/transmission assembly, wherein the swing arm mounts pivotally to the second mount integrally with the engine/transmission unit, thereby allowing the swing arm unit to rotate around the first mount in substantially a vertical plane of the frame, but allowing no pivotal movement in any other plane or any translation movement in any direction relative to the frame.
In various embodiments of the invention taught in enabling detail below, for the first time a system is provided that allows efficient mounting of an engine assembly in a motorcycle while eliminating many uncomfortable and dangerous effects that exist with conventional motorcycles as a result of having a rear mount with elastomeric elements that allow the rear wheel of the motorcycle to miss-align with the frame and the direction of travel of the motorcycle.